There is known, as the background art of the technical field of the present invention, JP-H11-186025-A (Patent Literature 1). Patent Literature 1 discloses as follows: “a superconducting coil has a structure such that a plurality of double-pancake coils is stacked. The double-pancake coils are stacked in a coil axial direction. Cooling plates are disposed between the respective double pancake coils. A plurality of springs is disposed in a circumferential direction so as to apply a pressure to the double-pancake coils in an axial direction.” There is also known, as the background art of the technical field of the present invention, JP-2012-209381-A (Patent Literature 2). Patent Literature 2 discloses “a superconducting device including: a superconducting coil; a refrigerator cooling the superconducting coil via a heat transfer path between the refrigerator and the superconducting coil; a vacuum container accommodating therein the superconducting coil and the refrigerator; and a pressure device that detects whether the refrigerator is in a steady operation state or in an abnormal state, and that forms the heat transfer path if detecting that the refrigerator is in the steady operation state and heat-insulates the superconducting coil from the refrigerator if detecting that the refrigerator is in the abnormal state, or a spring that applies a restoring force in a direction of heat-insulating the superconducting coil from the refrigerator when the pressure device malfunctions during power outage.”